Isolation Through Climate
Mountains create more isolation through climate, geological and disturbance diversity than lowlands and so often have more species, especially at middle elevations. The Klamath-Siskiyous also may have shielded life from the second worst disaster ever 65 million years ago. Even the timing was bad coming after and during great outpourings of carbon dioxide from Siberian volcanoes. North America was the worst hit, being covered by a lateral blast from a seven to ten mile wide asteroid traveling over 20 times faster than a bullet. First to spread across North America was a cloud of hot vaporized rock. Next was a tidal wave likely hundreds of times higher than the one in the Indian Ocean. Seawater probably washed over our continent except perhaps the top of the Klamath-Siskiyous-Belt Mountains.
When ejected rock fell red-hot back to earth, even wet wood burned for there was 10% more oxygen back then. Forests became ash except perhaps for serpentine and shale areas in the high Klamath-Siskiyous and Appalachians. A “nuclear winter” was followed by super-warming by carbon dioxide from vaporized rock. And we complain about our weather! Only one primate apparently survived, appropriately named Purgatorius.
Treeless or wet habitats may have saved some of our relict plants, such as darlingtonia, kalmiopsis, darmara and meadowfoam. Unfortunately we don’t know fossils or molecular clocks that could confirm this.
Remember when we were told that only cockroaches would survived a nuclear holocaust? Well, DNA indicates that the wood roach (Cryptocercus) began diverging from Appalachian roaches around this time, suggesting that the end-Cretaceous catastrophe created a big gap between the two populations for the first time.
Unlike the Gulf of Mexico crater, wood roaches are no smoking guns. Because the Klamath-Siskiyous may be the oldest continuous mountain systems in North America, it’s more likely that they accumulated diversity rather than being just a refuge at end-dinosaur times. The Appalachians should have accumulated more than our mountains because they rose earlier, but erosion reduced them to hills for a very long time. Our mountains’ great geo-diversity also provided thousands of habitats that not only increased speciation through isolation but also provided enough habitats for species to “hop over” to adjacent ones more suitable to them under a new climate, thus reducing extinctions.
If the dinosaur-killing asteroid was the second worst disaster for life, what’s the worst? That’s another topic, one on cave marble.